The formation and maintenance of normal tissue architecture and morphological pattern are dependent on cell-cell recognition and adhesion and adhesive interactions with extracellular biomatrix, complex processes which today are only partly understood. The research proposed herein will employ immunological methods to identify macromolecules involved in cell-cell adhesion which are present in material spontaneously shed or extracted from primary cultures of normal and regenerating hepatocytes, or transplantable hepatocellular carcinomata induced in ACI rats by 2-acetylaminofluorene. Adhesion will be measured by the rate of aggregation in suspension or the rate of contact formation by cells attached to collagen substrata. Cell adhesion molecules will be recognized by their ability to neutralize inhibition of cell adhesion by Fab fragments reactive against intact cells. Material exhibiting Fab-neutralizing activity will be fractionated by ion exchange, lectin-affinity, or gel chromatography, or by gel electrophoresis. Differential extracion techniques will be used to isolate components involved in cell-substrate adhesion. Putative cell adhesion molecules showing a high degree of homogeneity will be used to produce heteroantisera and/or monoclonal antibodies. Ultrastructural techniques will be used to characterize changes induced in primary cell or organ cultures by Fab fragments specific for cell adhesion molecules. Immunocytochemical techniques and cleavable bifunctional cross-linking agents will be used to examine the topographical relationships between cell adhesion molecules, microfilaments and other membrane macromolecules. Liposomes will be used to assess the adhesive activity of isolated membrane components. Lectin-affinity chromatography and SDS-polyacrylamide gel electrophoresis in combination with cell-surface specific radio-labeling techniques will be used for comparative analysis of cell adhesion molecules immunoprecipitated from NP-40 extracts of normal, regenerating and malignant hepatycytes. These studies should provide new information regarding the mechanism(s) of cellular adhesion and the role of this process in histotypic pattern formation of epithelial cells, thereby providing insight into cell-surface functions relevant to the expression of the malignant state.